Method for incenaration disposal of waste

ABSTRACT

There is provided a method of incinerating a waste material to process incineration residues produced in a gasification furnace easily with existing equipment. A combustible gas generated when a waste material A is dry-distilled in a gasification furnace  1  is introduced into a combustion furnace  3  and combusted therein. The combustible gas is generated in the gasification furnace  1  in order to keep the temperature in the combustion furnace  3  at a temperature capable of melting incineration residues. The incineration residues are charged into the combustion furnace  3  while the combustible gas is being combusted therein, and melted into a melted material B that is discharged from an outlet  3  of the combustion furnace  3  into a receptacle  33  in which the melted material B is solidified. Air supplied to an air jacket  6  and oxygen supplied to the gasification furnace  1  and the combustion furnace 3 are heated by a heat exchange with waste gases from the combustion furnace  3.  The heat exchange is carried out by providing a heat exchanger  36  with a conduit  8  disposed therein in a passage of the waste gases from the combustion furnace  4,  and passing air or oxygen through the conduit  8  upstream in the passage of the waste gases.

TECHNICAL FIELD

[0001] The present invention relates to a method of incinerating wastematerials.

BACKGROUND ART

[0002] The applicant of the present application has proposed anapparatus for incinerating waste materials such as waste tires asdisclosed in Japanese Laid-Open Patent Publication No. 2-135280. Withthe disclosed apparatus, a waste material is placed in a gasificationfurnace having a water jacket for preventing overheating, and a portionof the waste material is burned while the remainder of the wastematerial is subjected to dry distillation with the heat of combustion. Acombustible gas produced by the gasification furnace is introduced intoa combustion furnace outside the gasification furnace, in which thecombustible gas is burned. The temperature in the combustion furnace isdetected and the amount of oxygen supplied to the gasification furnace(specifically, oxygen required for partial combustion of the wastematerial) is adjusted depending on a change in the detected temperature,for thereby maintaining the temperature in the combustion furnacesubstantially at a predetermined temperature level. The predeterminedtemperature level is a temperature for causing the combustible gas toburn of its own accord, and is about 1000° C., for example. With thedisclosed apparatus, the amount of oxygen required to burn thecombustible gas in the combustion furnace is adjusted depending thedetected temperature in the combustion furnace, so that the amount ofoxygen commensurate with the amount of the combustible gas introducedinto the combustion furnace is supplied to the combustion furnace tocombust the combustible gas well in the combustion furnace.

[0003] The apparatus thus arranged is capable of incinerating the wastematerial while suppressing the emission of harmful gases into theatmosphere. Furthermore, since the combustible gas is combusted in thecombustion furnace at a substantially constant temperature while thewaste material is being subjected to dry distillation in thegasification furnace, the heat of combustion of the combustible gas caneffectively be utilized as a heat source for boiler apparatus, etc.

[0004] Incineration residues of waste materials such as municipal waste,sewage sludge, industrial waste, etc., including incineration residues(which are basically ashes, but may include waste not completely ashed)that are left in the gasification furnace after the dry distillation ofthe waste material in the gasification furnace, need to be disposed ofin a certain manner. According to one general process, afterincineration residues are taken out of the gasification furnace, theyare solidified with concrete, asphalt, etc. and disposed of.

[0005] However, objects to be disposed of according to the aboveprocess, including combustion wastes, are large in weight and volume andare difficult to handle. Since incineration residues may contain dioxinsand heavy metals, they may become a secondary pollution source dependingon where they are discarded.

[0006] According to another process, incineration residues are chargedinto a melting furnace which is held at a high temperature (e.g., a hightemperature of 1400° C. or higher) and melted therein, and the meltedincineration residues are cooled into a solid material.

[0007] When incineration residues are thus processed, dioxins containedtherein can be decomposed, and the solid material can effectively beused as a material of the aggregate for building and construction use.

[0008] According to the above other process, however, because themelting furnace for melting incineration residues and an apparatus forheating the melting furnace are required separately from thegasification furnace and the combustion furnace, the overall equipmentof the system for processing waste materials is large in size, and thecost required to introduce and maintain the equipment is high.

DISCLOSURE OF THE INVENTION

[0009] The present invention has been made in view of the abovebackground. It is an object of the present invention to provide a methodof incinerating a waste material to process incineration residuesproduced after the dry distillation of a waste material in agasification furnace is finished, easily with existing small-sizeequipment.

[0010] To achieve the above object, there is provided in accordance withthe present invention an improvement in a method of incinerating a wastematerial, having the steps of combusting a portion of the waste materialplaced in a gasification furnace and subjecting the other portion of thewaste material to dry distillation with heat produced by the combustionof the portion of the waste material, and introducing a combustible gasgenerated by the dry distillation into a combustion furnace disposedoutside said gasification furnace and combusting the combustible gas inthe combustion furnace, wherein oxygen required to combust thecombustible gas introduced into said combustion furnace is supplieddepending on the amount of the combustible gas into the combustionfurnace to combust the combustible gas, and the amount of oxygensupplied to said gasification furnace is controlled depending on achange in the temperature in the combustion furnace such that thetemperature in the combustion furnace is kept at a predeterminedtemperature, for thereby adjusting the amount of the combustible gasgenerated by the dry distillation. The method of incinerating a wastematerial according to the present invention is characterized in thatsaid predetermined temperature is set to a temperature at whichincineration residues produced when the waste material is incineratedare meltable, and is characterized by the steps of charging saidincineration residues into the combustion furnace from an incinerationresidue charging port thereof to melt the incineration residues with theheat generated when the combustible gas is combusted, while thecombustible gas is being combusted in said combustion furnace, anddischarging a melted material converted from the incineration residuesout of the combustion furnace from a melted material outlet thereof andcooling the melted material into a solid material.

[0011] With the above arrangement of the invention, since thepredetermined temperature in the combustion furnace at the time thecombustible gas is combusted therein is set to a temperature at whichthe incineration residues are meltable, while the combustible gas isbeing combusted in the combustion furnace, the amount of combustible gasgenerated in the gasification furnace is adjusted to keep thetemperature in the combustion furnace at the temperature at which theincineration residues are meltable. Therefore, when the incinerationresidues are charged into the combustion furnace from an incinerationresidue charging port thereof while the combustible gas is beingcombusted in the combustion furnace, the incineration residues aremelted in the combustion furnace with the heat of combustion of thecombustible gas. Thus, the combustion furnace for combusting thecombustible gas is used as a melting furnace to melt the incinerationresidues in the combustion furnace.

[0012] The temperature at which the incineration residues are meltableis generally 1400° C. or higher. When the incineration residues aremelted in the high-temperature environment, even if the incinerationresidues contain dioxins, the dioxins can be thermally decomposed. Ifthe incineration residues contain a waste material which has not beenfully ashed, then the waste material is completely combusted and ashedinto inorganic materials such as metals in the combustion furnace, andthose inorganic materials are thereafter melted.

[0013] According to the present invention, the melted material producedwhen the incineration residues are melted in the combustion furnace isdischarged out of the combustion furnace from a melted material outletthereof and cooled into a solid material.

[0014] The solid material thus produced when the melted material iscooled can be used as a material of the aggregate for building andconstruction use. Since the solid material is obtained from the meltedmaterial converted from the incineration residues, the solid material isnot larger or heavier than necessary, and can be handled, e.g.,transported, with ease.

[0015] The melted material discharged out of the combustion furnace maybe cooled with air or water. For increasing the strength and rigidity ofthe solid material, it is preferable to cool the melted material slowly.

[0016] According to the present invention, as described above, inasmuchas the incineration residues are melted in the combustion furnace inwhich the combustible gas generated in the gasification furnace iscombusted and the melted material is discharged out of the combustionfurnace and then cooled, no dedicated melting furnace is required formelting the incineration residues, and the incineration residues caneasily be processed with a existing small-size facility.

[0017] The above incineration residues may be incineration residuesproduced after the waste material are dry-distilled in the gasificationfurnace, or may be incineration residues produced when various wastematerials such as municipal waste, sewage sludge, industrial waste, etc.are combusted.

[0018] According to the present invention, it is preferable to add afluxing agent to said incineration residues before the incinerationresidues are charged into said combustion furnace. The added fluxingagent lowers the melting point of the incineration residues to make theincineration residues meltable more easily. As much of the incinerationresidues is contained in the fluxing agent when the melted material issolidified, heavy metals, etc. contained in the incineration residuesare prevented from leaking out.

[0019] The melted material outlet is a location held in contact with theambient air and tends to decrease in temperature. Therefore, while themelted material is flowing out of the combustion furnace through themelted material outlet, the melted material is liable to be partiallysolidified within the combustion furnace near the melted materialoutlet.

[0020] According to the present invention, therefore, the combustionfurnace is heated to keep the temperature near said melted materialoutlet at said predetermined temperature with a heating means providedon said combustion furnace near said melted material outlet after saidcombustible gas starts to be combusted in said combustion furnace.

[0021] With the combustion furnace thus heated, the incinerationresidues melted in the combustion furnace can flow out of the combustionfurnace while being reliably held in a melted state.

[0022] According to the present invention, furthermore, saidincineration residues are gradually charged into said combustion furnaceafter the temperature in said combustion furnace rises to a temperatureclose to said predetermined temperature after the dry distillation ofsaid waste material is started in said gasification furnace.

[0023] Because the incineration residues are slowly charged bit by bitinto the combustion furnace, the incineration residues are smoothlymelted in the combustion furnace successively in the order charged intothe combustion furnace. Consequently, the incineration residues areprevented from being deposed in an insufficiently melted state in thecombustion furnace, and hence can reliably be melted in the combustionfurnace.

[0024] The temperature at which the incineration residues are meltableis generally 1400° C. or higher. In order to keep the temperature in thecombustion furnace at the above temperature, the amount the combustiblegas introduced from the gasification furnace into the combustion furnace(specifically, the amount the combustible gas introduced into thecombustion furnace per unit time) has to be large. Basically, if theamount of oxygen supplied to the gasification furnace (oxygen requiredfor partial combustion of the waste material in the gasificationfurnace) is increased to increase the portion of the waste materialcombusted in the gasification furnace, then a large amount of drydistillation gas can be generated in the gasification furnace andintroduced into the combustion furnace. However, if the amount of wastematerial in the gasification furnace is small, then since the portion ofthe waste material which can be dry-distilled is reduced in a shortperiod of time, it is difficult to keep the temperature in thecombustion furnace at a high level capable of melting a sufficientamount of incineration residues. If the amount of waste material in thegasification furnace is increased, then the gasification furnace has tobe large in size.

[0025] According to the present invention, the method is characterizedin that said gasification furnace comprises an air-cooled gasificationfurnace.

[0026] If the gasification furnace is a conventional water-cooledgasification furnace having a water jacket, then though it is highlyeffective to prevent overheating, the amount of heat removed by anexterior medium, specifically water flowing through the water jacket, islarge, suppressing the dry distillation of the waste material. Accordingto the present invention, the amount of heat removed by an exteriormedium is reduced as the gasification furnace comprises an air-cooledgasification furnace.

[0027] According to the present invention, in order to prevent thegasification furnace from being overheated, the method is characterizedin that air heated by a heat exchange with waste gases from saidcombustion furnace is supplied to cool said gasification furnace. Withthis arrangement, the amount of heat removed by an exterior medium isfurther reduced.

[0028] As a result, much of the heat generated by the partial combustionof the waste material is used for dry distillation of the other portionof the waste material (the portion of the waste material which is notcombusted) in the gasification furnace, and the waste material consumedby the partial combustion is reduced whereas the waste material that isdry-distilled is increased. Therefore, it is possible to keep relativelysmall the total amount of waste material in the gasification furnace andportion thereof which is combusted, and at the same time to generate anamount of combustible gas large enough to increase the temperature inthe combustion furnace to a high temperature at which the combustiblegas is meltable. It is also possible to generate the large amount ofcombustible gas continuously for a relatively long period of time.Stated otherwise, it is possible to keep the temperature in thecombustion furnace at a high temperature at which the combustible gas ismeltable, for a relatively long period of time.

[0029] According to the present invention, the method is characterizedin that oxygen heated by a heat exchange with waste gases from saidcombustion furnace is supplied to said gasification furnace and/or saidcombustion furnace.

[0030] With the above arrangement, in the gasification furnace, theportion of the amount of heat generated by the partial combustion of thewaste material, which portion is absorbed by the oxygen supplied to thegasification furnace, is reduced. As a result, much of the heat is usedfor dry distillation of the other portion of the waste material, and thewaste material consumed for partial combustion is reduced whereas thewaste material which is dry-distilled is increased.

[0031] In the combustion furnace, the portion of the amount of heatgenerated by the combustion of the combustible gas, which portion isabsorbed by oxygen supplied to the combustion furnace, is reduced.Therefore, the amount of combustible gas required to keep thetemperature in the combustion furnace at a high level may be small. As aresult, it is possible to keep the temperature in the combustion furnaceat a high temperature at which the incineration residues are meltablefor a longer period of time. The gasification furnace may thus be of arelatively small size, and the combustion furnace can smoothly melt asufficient amount of incineration residues.

[0032] According to the present invention, the method is characterizedin that the heat exchange for air for cooling the gasification furnaceor oxygen supplied to the gasification furnace and/or the combustionfurnace is carried out by providing a heat exchanger with an air conduitor an oxygen conduit disposed therein in a passage of the waste gasesfrom said combustion furnace, and passing air or oxygen through the airconduit or the oxygen conduit upstream in the passage of the wastegases. The flow of the waste gases and the flow of the air or oxygenpassing through the air conduit or the oxygen conduit are directedopposite to each other. The air or oxygen is initially heated by a heatexchange with the waste gases at a relatively low temperature, and thenfurther heated by a heat exchange with the waste gases at a relativelyhigh temperature. Thus, an excellent heat exchange efficiency isachieved.

[0033] The heat exchange makes it unnecessary to use a dedicated heatsource for heating the air or oxygen, and effectively utilizes heatenergy generated in the combustion furnace.

[0034] According to the present invention, air supplied to cool saidgasification furnace is used as part of oxygen supplied to saidgasification furnace and/or said combustion furnace, after having cooledsaid gasification furnace. With this arrangement, the amount of heatremoved by an exterior medium is further reduced, and the heat generatedby the gasification furnace and the combustion furnace can be recycledefficiently.

[0035] According to the present invention, the air heated by the wastegases from the combustion furnace is supplied to cool the air-cooledgasification furnace, the oxygen heated by the waste gases from thecombustion furnace is supplied to both the gasification furnace and thecombustion furnace, and the cooling air supplied to the gasificationfurnace is used as part of oxygen supplied to said gasification furnaceand said combustion furnace, thus making it possible to easily achieve ahigh temperature at which the incineration residues are meltable in thecombustion furnace.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a diagram showing a system arrangement of an apparatusfor gasifying and incinerating a waste material by way of drydistillation, which is used in an embodiment of the present invention;

[0037]FIG. 2 is a graph showing the temperature in a gasificationfurnace and the temperature in a combustion furnace as they change withtime in a basic operation of the apparatus shown in FIG. 1;

[0038]FIG. 3 is a graph showing the temperature in the gasificationfurnace and the temperature in the combustion furnace as they changewith time in the apparatus shown in FIG. 1 according to an inventiveexample; and

[0039]FIG. 4 is a graph showing the temperature in the gasificationfurnace and the temperature in the combustion furnace as they changewith time in the apparatus shown in FIG. 1 according to a comparativeexample.

BEST MODE FOR CARRYING OUT THE INVENTION

[0040] As shown in FIG. 1, an apparatus for gasifying and incinerating awaste material by way of dry distillation according to an embodiment ofthe present invention has a gasification furnace 1 for placing therein awaste material A such as waste tires or the like, and a combustionfurnace 3 connected to the gasification furnace 1 by a gas passage 2.The gasification furnace 1 has a charge inlet 5 defined in an upper wallthereof and having an openable and closable charge door 4. The wastematerial A can be charged into the gasification furnace l through thecharge inlet 5. When the charge door 4 is closed, the interior space ofthe gasification furnace 1 is virtually isolated from the ambient space.

[0041] An air jacket 6 for being supplied with air for cooling thegasification furnace 1 to prevent the gasification furnace 1 from beingoverheated is disposed around the gasification furnace 1 in isolationfrom the interior space of the gasification furnace 1. The air jacket 6is connected by a cooling air supply passage 9 to a main air supplypassage 8 which extends from an air blower fan 7 serving as an airsupply outside the gasification furnace 1 and the combustion furnace 3.Air delivered from the air blower fan 7 to the main air supply passage 8is supplied via the cooling air supply passage 9 to the air jacket 6.

[0042] In the present embodiment, the air blower fan 7 serves to supplyair for cooling the gasification furnace 1 to the air jacket 6, and alsofunctions as an oxygen supply for supplying combustive oxygen(specifically air containing such oxygen) which is required to burn aportion of the waste material A in the gasification furnace 1 and acombustible gas, described later, in the combustion furnace 3. The airsupplied to the air jacket 6 is discharged from a discharge port, notshown, and circulated via an air retrieval passage 8a to the air blowerfan 7.

[0043] The gasification furnace 1 has a downwardly projectingfrustoconical lower wall surrounded by an empty chamber 10 isolated fromthe interior space of the gasification furnace 1 and the air jacket 6.The empty chamber 10 serves to supply oxygen (air) required to burn aportion of the waste material A in the gasification furnace 1 into thegasification furnace 1, and is held in communication with the interiorspace of the gasification furnace 1 through a plurality of air supplynozzles 11 mounted in an inner wall of the gasification furnace 1.

[0044] To the empty chamber 10, there is connected a first air supplypassage 12 branched from the main air supply passage 8. The emptychamber 10 is supplied with air containing oxygen which is deliveredfrom the air blower fan 7 into the main air supply passage 8, throughthe first air supply passage 12. The first air supply passage 12 has acontrol valve 13 for controlling the amount of air (the amount ofoxygen) supplied to the empty chamber 10. The control valve 13 iscontrolled for its opening by a valve actuator 14 which is controlled bya controller 15 comprising an electronic circuit including a CPU, etc.

[0045] An igniter 16 is mounted on a lower wall of the gasificationfurnace 1 for igniting the waste material A placed in the gasificationchamber 1 under operation control of the controller 15. The igniter 16comprises an ignition burner or the like and burns a fuel supplied froma fuel supply device 17 which stores a combustion assistant oil such askerosine or the like, thus supplying flames to the waste material A.Oxygen (air) required to burn the fuel in the igniter 16 is suppliedthrough a second air supply passage 19 branched from the main air supplypassage 8, by the air blower fan 7.

[0046] The combustion furnace 3 comprises a burner section 20 for mixinga combustible gas produced upon dry distillation of the waste material Aand oxygen (air) needed for complete combustion of the combustible gas,and a combusting section 21 for combusting the combustible gas which ismixed with oxygen. The combusting section 21 is held in communicationwith the burner section 20 downstream of the burner section 20. The gaspassage 2 is connected to an upstream end of the burner section 20 forintroducing the combustible gas produced upon dry distillation of thewaste material A in the gasification furnace 1 into the burner section20.

[0047] The burner section 20 has an empty chamber 22 defined in an outersurface thereof and isolated from the interior space of the burnersection 20. The empty chamber 22 serves to supply oxygen (air) to bemixed with the combustible gas, and is held in communication with theinterior space of the burner section 20 through a plurality of nozzleholes 23 defined in an inner circumferential wall of the burner section20. A third air supply passage 24 branched from the main air supplypassage 8 is connected to the empty chamber 22. The empty chamber 22 issupplied with oxygen (air) delivered from the air blower fan 7 into themain air supply passage 8, through the third air supply passage 24.

[0048] The third air supply passage 24 has a control valve 25 forcontrolling the amount of oxygen (the amount of air) supplied to theempty chamber 22. The control valve 25 is adjusted in its opening by avalve actuator 26 which is controlled by the controller 15, as with thecontrol valve 13 associated with the gasification furnace 1.

[0049] A combustor 27 is connected to the upstream end of the burnersection 20 for burning a combustion assistant oil supplied from the fuelsupply device 17 through a fuel supply passage 18. The combustor 27comprises an ignition burner or the like for burning the combustionassistant boil together with the combustible gas, if necessary, forwarming up in the combustion furnace 3 under operation control of thecontroller 15. The combustor 27 is also used to ignite the combustiblegas introduced into the burner section 20. Oxygen (air) required to burnthe fuel in the combustor 27 is supplied through a fourth air supplypassage 28 branched from the main air supply passage 8, by the airblower fan 7.

[0050] A residue chute 29 which serves as an incineration residuecharging port for charging incineration residues (not shown) of thewaste material into the combusting section 21 is mounted on a side wallof the combusting section 21 near the burner section 20. The residuechute 29 extends from outside the combustion furnace 3 obliquelydownwardly toward a furnace floor 30 of the combusting section 21.

[0051] The combusting section 21 has a projection 31 extending outwardlyfrom a lower side wall thereof remote from the burner section 20. Theprojection 21 has a melted material outlet 32 defined in a lower wallthereof for allowing a melted material B of the incineration residues toflow out of the combustion furnace 3. A melted material receptacle 33 isplaced below the melted material outlet 32 (outside the combustionfurnace 3) for storing and cooling the melted material B which hasflowed from the melted material outlet 32.

[0052] The furnace floor 30 of the combusting section 21 is slanted suchthat it is lower at the melted material outlet 32 than at the burnersection 20, as shown, for guiding the melted material B into the meltedmaterial outlet 32. The furnace floor 30 of the combusting section 21 ismade of chromium containing 25% or more of chromium in order to preventitself from being eroded by the melted material B at a high temperature.

[0053] A combustor 34 is mounted on the tip end of the projection 31 ofthe combusting section 21 for heating and keeping hot the interior spaceof the projection 31, i.e., a portion thereof near the melted materialoutlet 32. The combustor 34 comprises an ignition burner or the like andburns a combustion assistant oil supplied from the fuel supply device 17through the fuel supply passage 18 under operation control of thecontroller 15. Oxygen (air) required to burn the fuel in the combustor34 is supplied through a fifth air supply passage 35 branched from themain air supply passage 8, by the air blower fan 7.

[0054] A heat exchanger 36 is disposed downstream of the combustingsection 21. The heat exchanger 36 is held in communication with thecombusting section 21 and positioned in a passage of waste gases thatare generated by the complete combustion of the combustible gas in thecombusting section 21. The main air supply passage 8 has a helicallycoiled portion disposed in heat exchanger 36 and extending from an upperportion toward a lower portion thereof. As a result, in the heatexchanger 36, air passing through the main air supply passage 8 flowsupstream in the passage of waste gases, and is heated by a heat exchangethat is effected between the air and the waste gases that flow in thedirection opposite to the air.

[0055] A stack 37 is mounted on the upper end of the heat exchanger 36in communication with a downstream end of the heat exchanger 36. Thestack 37 has an inductive nozzle 39 for ejecting air supplied from anair blower fan 38 disposed outside the stack 37, upwardly in the stack37. The inductive nozzle 39 ejects the air supplied from the air blowerfan 38 upwardly in the stack 37 to induct the waste gases after theyhave performed the heat exchange in the heat exchanger 36, and dischargethe waste gases from the stack 37 into the atmosphere.

[0056] In the apparatus according to the present embodiment, atemperature sensor 40 for detecting a temperature T₁ in the gasificationfurnace 1 is mounted in an upper portion of the gasification furnace 1.A temperature sensor 41 for detecting a temperature T₂ in the combustionfurnace 3 is mounted in the combustion furnace 3 in facing relation tothe tip end of the burner section 20. Detected signals from thesetemperature sensors 40, 41 are inputted to the controller 15.

[0057] A basic operation sequence (in which the incineration residuesare not melted) of a method of incinerating waste materials which iscarried out by the apparatus according to the embodiment of the presentinvention will be described below with reference to FIGS. 1 and 2.

[0058] To incinerate a waste material A with the apparatus shown in FIG.1, the charge door 4 of the gasification furnace 1 is opened, and thewaste material A such as waste tires or the like is charged into thegasification furnace 1 through the charge inlet 5. Then, the charge door4 is closed to seal the gasification furnace 1, and a lower layer of thewaste material A is ignited by the igniter 16. When partial combustionof the waste material A begins, the temperature T₁ in the gasificationfurnace 1 which is detected by the temperature sensor 40 gradually risesup to a predetermined temperature T_(1A) (see FIG. 2), whereupon theigniter 16 is inactivated.

[0059] When the waste material A is ignited, the control valve 13 of thefirst air supply passage 12 is opened to a relatively small opening bythe valve actuator 14. As a result, the waste material A is ignitedusing oxygen present in the gasification furnace 1 and a small amount ofoxygen supplied from the air blower fan 7 through the main air supplypassage 8, the first air supply passage 12, and the empty chamber 10into the gasification furnace 1.

[0060] When the partial combustion of the lower layer of the wastematerial A in the gasification furnace 1 beings, the heat of combustionsets off dry distillation of an upper layer of the waste material A,producing a combustible gas that are introduced via the gas passage 2into the burner section 20 of the combustion furnace 3. After theignition of the waste material A, the opening of the control valve 13 ofthe first air supply passage 12 gradually increases, supplying the lowerlayer of the waste material A with an amount of oxygen that is requiredand sufficient to continuously burn the waste material A. As a result,the combustion of the waste material A is stabilized, but notunnecessarily expanded, in the lower layer thereof, and the drydistillation of the waste material A is stably carried out in the upperlayer thereof.

[0061] The combustor 27 of the combustion furnace 3 has been operatedprior to the ignition of the waste material A. When the combustible gasis introduced into the burner section 20, the temperature T₂ in thecombustion furnace 3 has been risen to 850° C. or higher, e.g., 870 C.°,for example. Even if the combustible gas contains dioxins, the dioxinsare thermally decomposed in the above temperature environment, and areprevented from being emitted into the atmosphere.

[0062] When the combustible gas is introduced into the burner section20, the control valve 25 of the third air supply passage 24 has beenopened to a predetermined opening by the valve actuator 26. Thecombustible gas is thus mixed with oxygen supplied from the third airsupply passage 24 through the empty chamber 22, and are ignited by thecombustor 27 and start to burn.

[0063] When the combustible gas starts to burn, the combustible gas maynot be supplied stably. However, as the dry distillation in thegasification furnace 1 is stabilized, as described above, thecombustible gas is continuously generated. As the generated amount ofcombustible gas increases, the temperature t₂ at which the combustiblegas is combusted in the combustion furnace 3 gradually increases asindicated by the imaginary curve in FIG. 2. The controller 15 adjuststhe flame power of the combustor 27 such that the temperature T₂ in thecombustion furnace 3 as detected by the temperature sensor 41 is kept at850° C. or higher. When the temperature t₂ at which the combustible gasis combusted reaches 850° C. or higher, the combustor 27 isautomatically inactivated, and the combustible gas is burned of its ownaccord.

[0064] When the combustible gas is burned of its own accord, thetemperature t₂ is brought into conformity with the temperature T₂ in thecombustion furnace 3 as detected by the temperature sensor 41. If thetemperature T₂ in the combustion furnace 3 as detected by thetemperature sensor 41 is lower than a preset temperature T_(2A), thenthe controller 15 increases the amount of oxygen supplied to thegasification furnace 1 to promote the dry distillation of the wastematerial A in the gasification furnace 1 for thereby increasing thegenerated amount of combustible gas. If the temperature T₂ is higherthan the preset temperature T_(2A), then the controller 15 reduces theamount of oxygen supplied to the gasification furnace 1 to suppress thedry distillation of the waste material A for thereby reducing thegenerated amount of combustible gas. The amount of oxygen supplied tothe gasification furnace 1 is thus controlled to automatically adjustthe amount of combustible gas generated in the gasification furnace 1 tokeep the temperature T₂ at the preset temperature T_(2A).

[0065] At the same time, until the temperature T₂ in the combustionfurnace 3 reaches the preset temperature T_(2A), the controller 15increases the opening of the control valve 25 to increase the amount ofoxygen supplied to the combustion furnace 3. After the temperature T₂has reached the preset temperature T_(2A), if the temperature T₂ dropsbelow the preset temperature T_(2A), then the controller 15 reduces theamount of oxygen supplied to the combustion furnace 3, and if thetemperature T₂ becomes higher than the preset temperature T_(2A), thenthe controller 15 increases the amount of oxygen supplied to thecombustion furnace 3. By thus controlling the amount of oxygen suppliedto the combustion furnace 3, an amount of oxygen required and sufficientto fully combust the combustible gas introduced from the gasificationfurnace 1 is supplied to the combustion furnace 3, allowing thecombustible gas to be fully combusted in the combusting section 21 ofthe combustion furnace 3.

[0066] The above control of the amount of oxygen supplied to thegasification furnace 1 and the combustion furnace 3 keeps thetemperature T₂ in the combustion furnace 3 substantially at the presettemperature T_(2A).

[0067] The temperature T₁ in the gasification furnace 1 as detected bythe temperature sensor 40 rises due to the partial combustion of thelower layer of the waste material A immediately after the waste materialA is ignited, and thereafter temporarily falls because the heat ofcombustion of the lower layer of the waste material A is consumed forthe dry distillation of the upper layer of the waste material A. Whenthe combustor 27 is inactivated and the combustible gas is combusted ofits own accord, the dry distillation enters a stage in which itprogresses stably and steadily (indicated as a stable dry distillationstage in FIG. 2), and the temperature T₁ gradually rises as the drydistillation progresses.

[0068] As the dry distillation of the waste material A progresses andthe portion of the waste material A which can be dry-distilled isreduced, the required amount of combustible gas cannot be produced evenwhen the amount of oxygen supplied into the gasification furnace 1 isincreased to maintain the temperature T₂ in the combustion furnace 3 atthe preset temperature T_(2A), and the amount of combustible gasintroduced into the combustion furnace 3 is gradually reduced. As aresult, the temperature T₂ in the combustion furnace 3 drops from thepreset temperature T_(2A). Shortly, the temperature t₂ at which thecombustible gas is burned also drops as indicated by the imaginary curvein FIG. 2. When the heat of combustion of the combustible gas alone isnot enough to keep the temperature T₂ in the combustion furnace 3 at thetemperature of 850° C. or higher, the combustor 27 is actuated again tokeep the temperature T₂ in the combustion furnace 3 at 850° C. orhigher.

[0069] When the portion of the waste material A which can bedry-distilled is eliminated and the waste material A is directly burned,the temperature T₁ in the gasification furnace 1 rises temporarilysharply as shown in FIG. 2. When any combustible portion of the wastematerial A is gone, the temperature T₁ in the gasification furnace 1begins to drop and gradually decreases as the waste material A is ashed(indicated as an ashing stage in FIG. 2). When the temperature T₁ in thegasification furnace 1 falls to a predetermined temperature T_(1B)(e.g., 200° C. or less) at which no dioxins are produced, since thetemperature T₂ in the combustion furnace 3 is no longer required to bekept at 850° C. or higher, the combustor 27 is inactivated. As a result,the temperature T₂ in the combustion furnace 3 is gradually lowered, andthe process of incinerating the waste material A is finished.

[0070] After the incinerating process is finished, the ashes of thewaste material A remain as the incineration residues in the gasificationfurnace 1. With the apparatus according to the present embodiment, theincineration residues are removed from an ash outlet, not shown, andcharged into the combustion furnace 3 and melted therein in a next cycleof operation.

[0071] An operation sequence of the apparatus according to the presentembodiment for melting the incineration residues simultaneously with theincineration of the waste material will be described below.

[0072] For melting the incineration residues, as with the basicoperation described above, the charge door 4 of the gasification furnace1 is opened, and the waste material A such as waste tires or the like ischarged into the gasification furnace 1 through the charge inlet 5.Then, the igniter 16 is actuated to ignite a lower layer of the wastematerial A. While the waste material A may be waste tires or the like,it may be mixed with a waste material such as waste plastics or the likein order to be able to generate a high-calorie combustible gas by way ofdry distillation.

[0073] The combustible gas generated by the dry distillation of thewaste material A in the gasification furnace 1 is introduced into thecombustion furnace 3, which starts to burn the combustible gas as withthe basic operation described above. In order to make the incinerationresidues (which are basically ashes, but may contain materials notcompletely ashed) meltable after the dry distillation of the wastematerial A in the gasification furnace 1, the temperature T₂ in thecombustion furnace 3 is set to a preset temperature which is higher thanthe normal preset temperature T_(2A). The preset temperature for makingthe incineration residues meltable (hereinafter referred to as “meltingpreset temperature”) is specifically set to 1400° C. or higher, e.g.,1450° C. (see FIG. 3).

[0074] In order to melt the incineration residues in the combustionfurnace 3, the incineration residues need to be charged into thecombustion furnace 3 while the temperature T₂ in the combustion furnace3 is being maintained at the melting preset temperature (e.g., 1450° C.)at which the incineration residues are meltable. For melting as muchincineration residues in the combustion furnace 3 as possible, it ispreferable to maintain the temperature T₂ in the combustion furnace 3 atthe melting preset temperature for as long a period of time as possible.Stated otherwise, it is preferable to produce, continuously for as longa period of time as possible, an amount of combustible gas large enoughto keep the temperature T₂ in the combustion furnace 3 at the meltingpreset temperature.

[0075] According to the present embodiment, air supplied to the airjacket 6 for cooling the gasification furnace 1, the interior space ofthe gasification furnace 1, and the burner section 20 of the combustionfurnace 3 is heated by the heat of waste gases produced when thecombustible gas is burned in the combustion furnace 3.

[0076] Specifically, air (at normal temperature in the presentembodiment) delivered from the air blower fan 7 into the main air supplypassage 8 passes through the heat exchanger 36 which is supplied withthe waste gases from the combustion furnace 3. Therefore, while thecombustible gas is being burned in the combustion furnace 3, the aboveair (containing oxygen) as it flows through the heat exchanger 36 isheated to a temperature of about 300° C., for example, by a heatexchange with the waste gases.

[0077] The heated air is supplied from the main air supply passage 8into the air jacket 6 of the gasification furnace 1, the interior spaceof the gasification furnace 1, and the burner section 20 of thecombustion furnace 3.

[0078] In the gasification furnace 1, therefore, the portion of theamount of heat generated by the partial combustion of the waste materialA upon the dry distillation, which portion is absorbed by the airsupplied to the air jacket and the air (oxygen) supplied to thegasification furnace 1 for the partial combustion of the waste materialA, may be reduced. As a result, much of the heat generated by thepartial combustion of the waste material A is small, the other portionof the waste material A is increased and sufficiently subject to drydistillation. Accordingly, it is possible to generate a combustible gascontinuously for a relatively long period of time, in an amount largeenough to keep the temperature T₂ in the combustion furnace 3 at themelting preset temperature.

[0079] Inasmuch as the temperature T₁ in the gasification furnace 1rises to a temperature higher than the temperature of the air suppliedto the air jacket 6 during dry distillation of the waste material A, thefurnace body of the gasification furnace 1 is sufficiently preventedfrom being overheated by the air.

[0080] In the combustion furnace 3, since the air (oxygen) heated asdescribed above is supplied to the burner section 2 and mixed with thecombustible gas, the portion of the amount of heat generated by thecombustion of the combustible gas, which portion is absorbed by the airsupplied to the burner section 20, may be small. As a consequence, theamount of combustible gas which is required to keep the temperature T₂in the combustion furnace 3 at the melting preset temperature may besmall.

[0081] As a result, as indicated by the imaginary curve in FIG. 3, thetemperature t₂ at which the combustible gas is combusted in thecombustion furnace 3 gradually increases toward the melting presettemperature. When the temperature t₂ reaches the melting presettemperature, the temperature T₂ in the combustion furnace 3 is kept atthe melting preset temperature in the same manner as the above basicoperation in which the temperature T₂ in the combustion furnace 3 iskept at the preset temperature T_(2A).

[0082] With the apparatus according to the present embodiment,therefore, the period of time for which the temperature T₂ in thecombustion furnace 3 is kept at the high melting preset temperature of1400° C. or higher, e.g., 1450° C., can be relatively long withoutspecially increasing the capacity of the gasification furnace 1 and theamount of waste material A placed therein. The incineration residues canbe melted in a sufficient quantity in the combustion furnace 3 withinthe period of time for which the temperature T₂ in the combustionfurnace 3 can be kept at the melting preset temperature.

[0083] In a process in which the temperature T₂ in the combustionfurnace 3 is increasing toward the melting preset temperature before thetemperature T₂ is kept at the melting preset temperature, if thetemperature T₂ in the combustion furnace 3 reaches a predeterminedtemperature T_(2B) (see FIG. 3), e.g., 1000° C., which is lower than themelting preset temperature, then the controller 15 operates thecombustor 34 mounted on the tip end of the projection 31 of thecombustion furnace 3 to start heating the interior space of theprojection 31 near the melted material outlet 32. Because the combustor34 starts operating at the predetermined temperature T_(2B) before thetemperature T₂ in the combustion furnace 3 reaches the melting presettemperature, the temperature in the projection 31 rises to a temperaturewhich is substantially equal to the melting preset temperature when thetemperature T₂ in the combustion furnace 3 as detected by thetemperature sensor 41 rises to the melting preset temperature.

[0084] Once the combustor 34 has started to operate, it is inactivatedwhen the temperature T₂ in the combustion furnace 3 becomes higher thanthe melting preset temperature. The combustor 34 is operated again whenthe temperature T₂ in the combustion furnace 3 drops below the meltingpreset temperature. In this manner, the temperature in the projection 31is kept at a temperature close to the melting preset temperature.

[0085] When the temperature T₂ in the combustion furnace 3 increases tothe melting preset temperature and is kept at the melting presettemperature (at a time S in FIG. 3), an incineration residue chargedevice such as a conveyor or the like (not shown) disposed outside thecombustion furnace 3 is activated by the controller 15 to charge theincineration residues (not shown) from the residue chute 29 into thecombusting section 21 of the combustion furnace 3.

[0086] A fluxing agent has been mixed with the incineration residues inorder to lower the melting point thereof. The fluxing agent may compriseone or a mixture of two or more of silicic acid, silicic acid compound,a material mainly containing silicic acid, boric acid, boric acidcompound, a material mainly containing boric acid, an alkali metalcompound, and an alkali earth metal compound.

[0087] The silicic acid compound or the material mainly containingsilicic acid may be silica sand, mountain sand, river sand, silicastone, diatomaceous earth, sodium silicate, magnesium silicate, glassdebris, clay, etc. The boric acid may be either orthoboric acid,metaboric acid, tetraboric acid, or boron oxide. The boric acid compoundor the material mainly containing boric acid may be orthoborate,metaborate, tetraborate, diborate, pentaborate, hexaborate, octaborate,borax, calcium borate, or the like.

[0088] The alkali metal compound may be soda ash, salt, caustic soda, orthe like. The alkali earth metal compound may be lime, slaked lime,limestone, or the like.

[0089] The residue chute 29 is closed by an openable and closable door,not shown, when no incineration residues are charged. The time S tostart charging the incineration residues is a predetermined time afterthe temperature T₂ in the combustion furnace 3 has reached the meltingpreset temperature, for example.

[0090] The incineration residues are gradually charged bit by bit fromthe residue chute 28 into the combusting section 21 of the combustionfurnace 3. At this time, the temperature T₂ in the combustion furnace 3is kept substantially at the melting preset temperature (e.g., 1450° C.)at which the incineration residues are melted. The incineration residueshave been mixed with a fluxing agent such as silica sand or limestonefor lowering the melting point thereof. Therefore, each time theincineration residues are charged, the incineration residues are quicklymelted into a melted material B in the combusting section 21 of thecombustion furnace 3. If dioxins are contained in the incinerationresidues, then the dioxins are thermally decomposed when theincineration residues are melted.

[0091] The melted material B which is produced when the incinerationresidues are melted flows on the furnace floor 30 of the combustingsection 21 toward the melted material outlet 32 in the projection 31,then flows out of the combustion furnace 3 through the melted materialoutlet 32, and drops into and is stored in the melted materialreceptacle 33. Since the interior space of the projection 31 is kept ata temperature close to the melting preset temperature, the meltedmaterial B is not cooled and solidified by ambient air when it flows outfrom the melted material outlet 32. Therefore, the incineration residuesmelted in the combustion furnace 3 (the melted material B) flow in theirentirety smoothly from the melted material outlet 32 into the meltedmaterial receptacle 33.

[0092] The melted material B stored in the melted material receptacle 33is slowly cooled and solidified into a solid material by natural aircooling. By cooling the melted material B slowly, the solid materialbecomes excellent in strength and rigidity, and can be used as a goodmaterial of the aggregate for building and construction use. As themelted material B contains vitreous silica sand, heavy metals containedin the incineration residues are well trapped in the solid material andprevented from leaking out.

[0093] Before the incineration residues are charged, the melted materialoutlet 32 is closed by an openable and closable door, not shown. Theamount of incineration residues to be charged into the combustionfurnace 3 and the time at which the incineration residues to be chargedinto the combustion furnace 3 are adjusted in advance such that themelting of the incineration residues and the flowing of the meltedmaterial B out of the melted material outlet 32 are completed while thetemperature T₂ in the combustion furnace 3 is being continuously kept atthe melting preset temperature, When the portion of the waste material Awhich can be dry-distilled is eliminated and the waste material A isdirectly burned, and the combustible portion of the waste material A isgone, thus entering the ashing stage, the temperature T₁ in thegasification furnace 1 and the temperature T₂ in the combustion furnace3 are gradually lowered, putting the process of incinerating the wastematerial A to an end as with the basic operation described above. Afterthe incinerating process is finished, the incineration residues of thewaste material A are removed from the ash outlet (not shown) of thegasification furnace 1, and charged into the combustion furnace 3 andmelted therein in a next cycle of operation.

[0094] According to the present embodiment, as described above, since asufficient amount of incineration residues can be melted in thecombustion furnace 3, no dedicated melting furnace is required, and thewaste material A can be incinerated and the incineration residues canthereafter be processed (melted and solidified) efficiently with asmall-size, simple facility which employs the existing gasificationfurnace 1 and the existing combustion furnace 3.

[0095] In the above embodiment, incineration residues produced after thewaste material A are dry-distilled in the gasification furnace 1 areemployed as the incineration residues to be introduced into thecombustion furnace 3. However, incineration residues produced when wastematerials such as municipal waste, sewage sludge, industrial waste, etc.are combusted may be employed as the incineration residues to beintroduced into the combustion furnace 3.

[0096] In the present embodiment, the stack 37 is provided incommunication with the heat exchanger 36 for discharging waste gasesused to heat air with the heat exchanger 36 immediately from the stack37 into the atmosphere. However, a duct may be disposed downstream ofthe heat exchanger 36 for guiding waste gases through the duct to thestack 37. A cyclone, a cooling tower, a bug filter, etc. may be providedin the duct for trapping and removing dust and ashes contained in thewaste gases. With such a modification, the air blower fan 38 and theinductive nozzle 39 may be disposed in the duct in front of the stack37.

[0097] In the present embodiment, the air heated by the heat exchanger36 is supplied to the air jacket 6, the gasification furnace 1, and thecombustion furnace 3 after the combustible gas starts being combusted inthe combustion furnace 3. However, the heated air may be supplied to theair jacket 6 and the gasification furnace 1 before the waste material Ais ignited in the gasification furnace 1. In the combustion furnace 3,before the waste material A is ignited, the combustor 27 is operated toburn the combustion assistant oil to increase the temperature T₂ in thecombustion furnace 3 to 850° C. or higher. The heat produced by burningcombustion assistant oil heats the air which is introduced from the mainair supply passage 8 into the heat exchanger 36. In this manner, thetime required until the dry distillation in the gasification furnace 1is stabilized can be shortened, and it is possible to generate anincreased amount of combustible gas.

[0098] Inventive and comparative examples of the present invention willbe described below.

INVENTIVE EXAMPLE

[0099] In the inventive example, the apparatus shown in FIG. 1 was used,and after the waste material A in the gasification furnace 1 wasignited, the air heated by the heat exchanger 36 was supplied to the airjacket 6, the gasification furnace 1, and the combustion furnace 3, thusincinerating the waste material A and melting the incineration residues.The incineration residues were produced in advance by incinerating thewaste material A with the apparatus shown in FIG. 1.

[0100] In the inventive example, the melting preset temperature was setto 1450° C., and the temperature of the heated air was about 300° C. inincinerating the waste material A and melting the incineration residues.

[0101] As a result, in the inventive example, as shown in FIG. 3, whenthe process entered the stable dry distillation stage, the temperatureT₂ in the combustion furnace 3 easily reached the melting presettemperature and was continuously kept substantially at the meltingpreset temperature, so that a sufficient amount of incineration residuescould be melted.

COMPARATIVE EXAMPLE

[0102] In the comparative example, the apparatus shown in FIG. 1 wasmodified such that the main air supply passage 8 bypassed the heatexchanger 36 from the inlet to the outlet thereof and did not passthrough the heat exchanger 36, and the waste material A was incineratedand the incineration residues were melted in the same manner as theinventive example. In the comparative example, air supplied at thenormal temperature from the air flow fan 7 was introduced into the airjacket 6, the gasification furnace 1, and the combustion furnace 3,which were not supplied with any heated air.

[0103] As a result, in the comparative example, as shown in FIG. 4, whenthe process entered the stable dry distillation stage, the temperatureT₂ in the combustion furnace 3 did not easily reach the melting presettemperature and was kept at the melting preset temperature only for abrief period of time. Therefore, the incineration residues could hardlybe melted.

[0104] It will be seen from the above inventive and comparative examplesthat when the air heated by the heat exchanger 36 is supplied to the airjacket 6, the gasification furnace 1, and the combustion furnace 3 toincinerate the waste material A, the temperature T₂ in the combustionfurnace 3 can easily be brought to a high temperature of 1450° C. formelting the incineration residues, and can be maintained continuously atthe high temperature for a long period of time.

[0105] In the inventive example, after the waste material A in thegasification furnace 1 was ignited, the heated air was supplied to theair jacket 6, the gasification furnace 1, and the combustion furnace 3.However, when the heated air was supplied to the air jacket 6 and thegasification furnace 1 before the waste material A was ignited, the timerequired for the temperature T₂ in the combustion furnace 3 to reach themelting preset temperature was shorter than the time in the inventiveexample. Furthermore, the temperature T₂ in the combustion furnace 3 waskept at the melting preset temperature for a longer period of time thanthe period of time in the inventive example.

[0106] Industrial Applicability:

[0107] According to the present invention, at the same time that a wastematerial such as waste tires or the like is incinerated, incinerationresidues of waste materials such as municipal waste, sewage sludge,industrial waste, etc. are melted, and the melted incineration residuescan be cooled and solidified.

1. A method of incinerating a waste material, having the steps ofcombusting a portion of the waste material placed in a gasificationfurnace and subjecting the other portion of the waste material to drydistillation with heat produced by the combustion of the portion of thewaste material, and introducing a combustible gas generated by the drydistillation into a combustion furnace disposed outside saidgasification furnace and combusting the combustible gas in thecombustion furnace, wherein oxygen required to combust the combustiblegas introduced into said combustion furnace is supplied depending on theamount of the combustible gas into the combustion furnace to combust thecombustible gas, and the amount of oxygen supplied to said gasificationfurnace is controlled depending on a change in the temperature in thecombustion furnace such that the temperature in the combustion furnaceis kept at a predetermined temperature, for thereby adjusting the amountof the combustible gas generated by the dry distillation, said methodbeing characterized in that, said predetermined temperature is set to atemperature at which incineration residues produced when the wastematerial is incinerated are meltable, said method further comprising thesteps of: charging said incineration residues into the combustionfurnace from an incineration residue charging port thereof to melt theincineration residues with the heat generated when the combustible gasis combusted, while the combustible gas is being combusted in saidcombustion furnace, and discharging a melted material converted from theincineration residues out of the combustion furnace from a meltedmaterial outlet thereof and cooling the melted material into a solidmaterial.
 2. A method of incinerating a waste material according toclaim 1, characterized by the step of adding a fluxing agent to saidincineration residues before the incineration residues are charged intosaid combustion furnace.
 3. A method of incinerating a waste materialaccording to claim 1 or 2, characterized by the step of heating thecombustion furnace to keep the temperature near said melted materialoutlet at said predetermined temperature with a heating means providedon said combustion furnace near said melted material outlet after saidcombustible gas starts to be combusted in said combustion furnace.
 4. Amethod of incinerating a waste material according to any one of claims 1through 3, characterized in that said incineration residues aregradually charged into said combustion furnace after the temperature insaid combustion furnace rises to a temperature close to saidpredetermined temperature after the dry distillation of said wastematerial is started in said gasification furnace.
 5. A method ofincinerating a waste material according to any one of claims 1 through4, characterized in that said gasification furnace comprises anair-cooled gasification furnace.
 6. A method of incinerating a wastematerial according to claim 5, characterized by the step of supplyingair heated by a heat exchange with waste gases from said combustionfurnace, to cool said gasification furnace.
 7. A method of incineratinga waste material according to claim 6, characterized in that said heatexchange is carried out by providing a heat exchanger with an airconduit disposed therein in a passage of the waste gases from saidcombustion furnace, and passing air through said air conduit upstream inthe passage of the waste gases.
 8. A method of incinerating a wastematerial according to any one of claims 1 through 7, characterized bythe step of supplying oxygen heated by a heat exchange with waste gasesfrom said combustion furnace, to said gasification furnace and/or saidcombustion furnace.
 9. A method of incinerating a waste materialaccording to claim 8, characterized in that said heat exchange iscarried out by providing a heat exchanger with an oxygen conduitdisposed therein in a passage of the waste gases from said combustionfurnace, and passing oxygen through said oxygen conduit upstream in thepassage of the waste gases.
 10. A method of incinerating a wastematerial according to any one of claims 5 through 9, characterized inthat air supplied to cool said gasification furnace is used as part ofoxygen supplied to said gasification furnace and/or said combustionfurnace, after having cooled said gasification furnace.